This invention relates to a fuel injection system for an engine and more particularly to an improved air/fuel injection system.
It is known that the performance of many engines can be improved by employing fuel injection systems and particularly direct fuel injection systems. For example, it has been found that the efficiency and emission control of a crankcase compression, two-cycle engine can be improved if direct cylinder fuel injection is employed. However, the use of such direct injected systems gives rise to certain problems.
For example, during the engine operation, there is a wide variance of speed and load ranges under which the engine must operate. This is particularly true when the engine is employed as a power plant for a vehicle. To provide a fuel injection system for an engine wherein all of the fuel supply requirements can be supplied and accurately controlled can be extremely expensive. That is, if a single fuel injector is employed for providing all of the fuel requirements of the engine regardless of its operating condition, very expensive injectors and control systems may be required.
It is, therefore, a principal object of this invention to provide an improved fuel injection system for an internal combustion engine.
It is a further object of this invention to provide an injection system for an internal combustion engine that will adequately supply and control the fuel requirements under all running conditions and yet which will be low in cost.
The type of fuel injectors that inject not only fuel but air under pressure into the combustion chamber have been known for a long period of time. Under certain applications, such air and fuel injection may be desirable. However, the use of an injector that injects both air and fuel provides a more complicated and bulky system. It has been found that the range of fuel control for the engine can be improved if a pair of fuel injectors are employed for meeting the maximum fuel requirements and also providing accurate control under low speed conditions. However, when two fuel injectors are employed and an air fuel injection system is incorporated, the system can be extremely bulky and difficult to incorporate into an engine.
It is, therefore, a still further object of this invention to provide an improved air/fuel injector for an internal combustion engine which has a simple compact construction.
In conjunction with direct cylinder injection, the pressure of the fuel that is discharged into the combustion chamber must, of course, be greater than the pressure that is existent within the combustion chamber. That is, the amount of fuel sprayed will be dependent to some extent on the pressure difference between the pressure discharged from the injector and the pressure in the combustion chamber. However, as the piston approaches top dead center, the compression pressure in the cylinder will rise abruptly and it is therefore desirable to complete the fuel injection before the pressure rises significantly. This is particularly important in conjunction with air/fuel injectors wherein the air pressure may be relatively limited in relation to actual compression pressures. Of course, there is a practical limit in the time at which injection can be started and, therefore, the actual time interval during which fuel injection can be accomplished in the cylinder is somewhat limited with respect to crank angle.
It is, therefore, a further object of this invention to provide a fuel injector that will insure that adequate fuel can be injected into the engine before the compression pressure becomes too high.
It is a further object of this invention to provide an improved fuel injector of the air/fuel type wherein the amount of fuel injected before compression pressure becomes too high can be substantial under high speed running conditions without losing control at low speed conditions.